Stair structure



April 22, 1941. WCHAUD ETAL 2,239,428

STAIR STRUCTURE Filed Jan. 18, 1940 2 Sheets-Sheet 1 FM 5 7 U M 52AM Vjwflw 5 April 22, 1941. MlCHAUD ETAL 2,239,428

STAIR STRUCTURE Filed Jan. 18, 1940 2 Sheets-Sheet 2 5:5 Henry 19.,Michorucf I J mes A, M clvcrud Patented Apr. 22, 1941 UNITED STATESPATENT OFFICE STAIR STRUCTURE Henry A. Michaud and James A. Michaud,

Hodge, La.

Application January 18, 1940, vSerial No. 314,424

4 Claims. (Cl. 72-96) This invention relates to stair structure built upof units of reinforced concrete intimately fitted and joined together toprovide a comparatively light but durable and efficient stairway.

An important object of the invention is to provide stringer units ofreinforced concrete and adapted to be secured to a support and providinghorizontal and vertical surfaces for step tread and riser parts.

Another important object of the invention is to provide step units eachin the form of a reinforced concrete casting to provide tread parts andriser parts for engaging respectively with the tread and riser surfacesof the stringer units.

A further important object is to provide improved joints andinter-fitting engagement of the units so that they will rigidly be heldagainst lateral displacement or tipping.

A further important object is to provide improved reinforcements for thestep units comprising preferably transversely extending metal bars inthe tread portions and vertical bars in the riser portions, with thehorizontal and vertical bars forming a rigid integral reinforcingstructure as by being welded together, such metal reinforcement thenrelieving the concrete of strain and strengthening the step unitsagainst breakage.

Still another important object is to utilize the rear ends of thehorizontal reinforcing bars of a tread part to be engaged by the riserpart of the next step unit so that the step units will be held down attheir rear ends against tipping under weight on the projecting noseportions of the treads which overhang the risers.

The invention also embodies other improved features of construction andarrangement, and all the features of the invention are incorporated inthe structure shown on the drawings, on which drawings:

Figure 1 is a perspective view of our improved stair structure and partof a supporting structure to which the stair structure is applied;

Figure 2 is a transverse section of the stair structure;

Figure 3 is a section on plane III-III Figure 2;

Figure 4 is a section on plane IV-IV Figure 2;

Figure 5 is a section on plane V-V Figure 3;

Figure 6 is a section on plane VIVI Figure 3;

Figure 7 is the rear end view of one of the stringer units showing asupporting plate anchored to the stringer; and

Figure Bis an enlarged view of the horizontal and vertical reinforcingbars of a step unit, welded together.

The stair structure shown comprises the stringer units A and the stepunits B. The stringer units, when in service, extend diagonallydownwardly from a support to the ground. Figure 1 shows the stringersextending downwardly from a support structure S to the ground. At theirinner ends, the stringers have the vertical faces I0 for engagingagainst the support, and at their lower ends the stringers have thehorizontal surfaces 1 I for engagement with the ground or with a base orfoundation block l2 of concrete laid in the ground. Metal reinforcingrods or bars I 3 extend through each stringer unit for strengthening theconcrete, and on their upper sides the stringer units are shaped toprovide the horizontal tread receiving surfaces I4 and the verticalriser receiving surfaces l5.

A metal plate or bracket I6 is secured to the inner end ID of eachstringer and preferably set into a recess I1, and anchor rods l3 extendfrom the plate to be embedded in the concrete, the rods preferablyhaving hooked inner ends and are rigidly secured to the plate as byriveting or welding. These plates at their inner ends have holes IQ forreceiving screws or bolts 20 for engagement with a support such as thesupport S, whereby the stringers may be rigidly secured at their upperends to the supports.

Each step unit B is cast integral of concrete and comprises a tread 2|and a riser 22. Each tread has a number of longitudinally extendingreinforcing metal bars 23 extending therethrough, and each tread mayhave one or more longitudinally extending reinforcing bars 24 extendingtherethrough. Each tread has a number of transverse reinforcing bars 25therein and each tread has a number of transverse reinforcing bars 26.

Each tread 21 at its front extends a distance beyond to overhang thecorresponding riser as indicated at 21, and the cross bars 25 in thetread extend well into the overhanging part 21 so as to strengthen thispart. The transverse bars 26 of the risers meet the transverse bars 25of the treads and are rigidly secured thereto as by welding so that thesecured together bars provide rigid substantially T-shaped metalreinforcing structures for the step units to relieve the concrete ofoverstrain which might cause cracking or breakage thereof, particularlyat the juncture of the tread and riser elements, when the units aresubjected to bumps or blows during shipment or handling thereof. ihereinforcing structures could be formed by bending a length of bar toform horizontal and vertical legs, but by welding the riser reinforcingbars to the tread bars at an intermediate point thereof, the outer endsof the riser bars will afford strengthening for the overhanging or noseportions 21 of the treads.

The step units are mounted on the stringers A, the treads being of awidth so that the risers of one step unit will engage between thecorresponding face l5 of the stringer and the rear edge of the tread ofthe next lower step unit. All or some of the transverse reinforcing bars25 of the treads may project rearwardly a distance provided to receivethe bar ends 25' when the stair is assembled so' that the risers willthen engage with the bars and one step unit will thus hold'the next stepunit down at its rear end to prevent tilting or tipping of the step unitparticularly under weight applied on the overhanging or nose portion 2'!of the step units. The step units are all cast in the same mold, and theends 25 of the cross reinforcing bars in the tread of the upper stepunit may be left and utilized to support the stair structure, or thisend may be cut off.

As indicated at 29, the lower inner corners of the risers are beveled tofit the correspondingly beveled corners of the stringers, thisarrangement widening the stringers at step corners and strengthening thestringers against cracking at the corners. The longitudinally extendinginner and outer corners between the treads and the risers are alsofilled in or beveled as indicated at 33, and the corners between theoverhanging ends of the treads and the ends of the corresponding risersare also beveled or filled in as indicated at 3! so that these cornersare strengthened to correspondingly increase the strength of connectionbetween the tread and riser.

The stringers at their tread receiving surfaces id have notches orgrooves 32 for receiving tongues 33 at the ends of the tread, thesetongue and groove connections holding the treads against forwardslipping on the stringers. At its rear end, each tread of the dependinglip or rib 3 forming an integral part thereof to extend lengthwiseon'the tread between the stringers, these lips or ribs increasing thethickness and strength of the treads at the back edges thereof and theribs also serve to hold the step unit against longitudinal slipping ordisplacement on the stringers. As best shown on Figure 5, the ends ofthe treads have the portions 35 extending downwardly along the outersides of the stringers below the stringer tread receiving tops M, andthese portions 35 also align the treads on the stringers and preventlateral or side slip of the step units on the stringers.

Where a concrete base block I2 is use-d for supporting the stairstructure at its lower end, this block may be recessed to provide sideabutments 3% for holding the stringers against lateral displacement, anda front abutment or shoulder 3'! against which the lower riser 22 abuts,the concrete block thus holding the stair structure against lateral andtransverse displacement at its lower end, so that with the concreteblock, and the screws or bolts 29, the stair structure will be rigidlylocated between a support such as S and the ground,

We have thus produced a very practical and emcient and economicallyconstructed stair structure, the stringer units and the step units beingeconomically molded or cast from concrete, and the units being quicklyand readily assembled, and when assembled will hold themselves in properposition and against displacement. We have shown one practical andefficient embodiment of the various features of our invention but we donot desire to be limited to the exact construction and arrangement shownand described as changes and modifications may be made without departingfrom the scope of the invention.

We claim as follows:

1. A stairway assembly comprising stringer elements of reinforcedconcrete and presenting tread and riser surfaces, integral step units ofreinforced concrete each comprising a tread element and a downwardlyextending riser element for application to the tread and riser surfacesof said stringers, 'said tread elements at their ends having dependingtongues and said stringers having grooves for receiving said tongueswhereby said step units will be held against forward displacement onsaid stringers, a reinforcing rib on the underside of each tread elementadjacent the rear edge thereof and extending between the inner sides ofthe stringers, said tread elements at their outer ends having dependingportions engaging with the outer sides of said stringers and cooperatingwith said reinforcing ribs to hold said step units against lateraldisplacement on said stringers, and metal brackets permanently rigidlyanchored to the upper ends of said stringore for attachment to a supportto which the stair assembly is to be applied.

2. A stairway assembly comprising stringer elements in the form ofprecast reinforced concrete units presenting tread and riser surfaces,integral step units precast of concrete and each comprising a tread partand a downwardly extending riser part for engaging the tread and risersurfaces of the stringers, said tread parts extending a distance beyondthe respective riser parts to overhang said riser parts, transverselyextending reinforcing metal rods in said tread parts extending into theoverhanging portions thereof, transversely extending reinforcing rods inthe riser parts welded at their upper ends to the tread part reinforcingrods at points intermediate the ends of said tread part rods whereby toform rigid T-shaped reinforcing structures for the step units, thereinforcing bars of the tread parts projecting a distance rearwardlybeyond the rear edges of the tread parts and the risers having notchesin their lower ends whereby when the step units are assembled on thestringers said riser notches will receive the projectingends of thereinforcing rods and tipping of the step structures will be prevented,and cooperating abutments on the tread parts and stringers for holdingthe step units against lateral displacement on the stringers.

3. A stair assembly comprising spaced apart stringers each in the formof a precast reinforced concrete unit presenting tread and riserreceiving surfaces, integral step units each precast of concrete andcomprising a tread element and a downwardly extending riser element forengaging the tread and riser surfaces on the stringers, the width of thetread elements being such that the riser of one step unit will engage atits lowerend behind the tread element of the next lower step unit,transversely extending reinforcing metal rods in the tread elements andprojecting a distance rearwardly beyond the rear ends of said elements,the riser elements at their lower edges being notched whereby when thestep units are assembled on the stringers the riser notches of one unitwill receive the projecting ends of the reinforcing tread bars of thenext lower unit to hold the next lower unit against tipping, andcooperating abutments on the said elements and stringers for holdingsaid step units against lateral displacement.

4. In a stair assembly, a precast concrete step unit comprising ahorizontal tread element and a vertical riser element set inwardly adistance from the front edge of the tread element, integral T-shapedmetal reinforcing bars having their vertical legs embedded in said riserelement and their horizontal legs embedded in the tread element, therear ends of the horizontal legs of said reinforcing structuresprojecting a distance rearwardly beyond the rear edge of the treadelement and the riser element having cross slots in its lower edge inalignment with said projecting ends whereby when step units areassembled to form a stair the cross slots of one riser will receive theprojecting ends of the reinforcing structures of the next lower treadunit.

HENRY A. MICHAUD. JAMES A. MICI-IAUD.

